doubt about 'bool is_executing'

[Sebastian Huber]

On 28/07/2021 21:54, Gedare Bloom wrote:
> Hello all,
> 
> In most (all?) the SMP ports, we have in the CPU Context Control:
>    bool is_executing;

Yes, all SMP ports need this. It is used to implement a TTAS lock in the 
context switch:

https://docs.rtems.org/branches/master/c-user/symmetric_multiprocessing_services.html#thread-dispatch-details

> 
> This variable often is accessed through assembly language (i.e.,
> during the context switch), using something like
> ARCH_CONTEXT_CONTROL_IS_EXECUTING_OFFSET. Unfortunately, the 'bool'
> type is not standard, or rather its size is implementation-defined.  I
> think it is generally an 8-bit value though for us. I see that the
> riscv port uses explicitly a uint32_t so that's nice.
> 
> I think we should replace 'bool' with uint8_t in the other ports that
> are using byte-size accesses from assembly, just to be well-defined.
> Most likely, this doesn't actually affect anything and I'm just a
> little paranoid.

Is the bool size and alignment not defined by the ABI? We don't have to 
use this type, we could also use an uint32_t or whatever. The convention 
is that a zero value is false, everything else is true.

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